Vehicles are receiving an increasing number of wireless services, such as cellular phone service, satellite radio, terrestrial radio, and Global Positioning System (GPS) service. As additional wireless services become available, a vehicle must be equipped to accommodate the different types of signals. Multi-band antennas are widely used in vehicles. When designing multi-band antennas, designers focus on cost, aesthetics, and aerodynamics.
Conventional multi-band antennas have a single receiving element with a broad bandwidth and are designed to receive signals from all bands of interest. However, it is difficult to make a single receiving element receive multiple bands because each wireless service requires a different radiation pattern.
Other multi-band antennas have a single module that includes multiple antenna receiving elements. Each antenna element receives a different service at a given frequency. The signals received by each antenna element are sent to different receivers using separate cables. However, as the number of cables increases, the cost increases. Additionally, certain combinations of antenna receiving elements can cause interference.
In addition to cost, the overall dimensions of the antenna are important. A large number of antenna receiving elements increases the size of the antenna module. As the size increases, the aerodynamic drag increases, which may cause wind noise and/or reduce fuel economy.